IMO Mule is basically a container-type framework that rests on various open source products...
if you go to the 1.4.1 distribution's opt folder the listing is as such:
05/22/2007 08:23a 444,463 acegi-security-1.0.1.jar 05/22/2007 08:28a 443,432 antlr-2.7.6.jar 05/22/2007 08:26a 1,599,570 axis-1.4.jar 05/22/2007 08:26a 31,191 axis-jaxrpc-1.4.jar 05/22/2007 08:26a 18,979 axis-saaj-1.4.jar 05/22/2007 08:26a 126,771 axis-wsdl4j-1.5.1.jar 05/22/2007 08:21a 327,810 backport-util-concurrent-3.0.jar 05/22/2007 08:28a 490,136 c3p0-0.9.0.4.jar 05/22/2007 08:23a 193,391 carol-2.0.5.jar 05/22/2007 08:28a 324,238 cglib-nodep-2.1_3.jar 05/22/2007 08:26a 36,342 commons-attributes-api-2.1.jar 05/22/2007 08:21a 188,671 commons-beanutils-1.7.0.jar 05/22/2007 08:21a 30,117 commons-cli-1.0.jar 05/22/2007 08:23a 46,725 commons-codec-1.3.jar 05/22/2007 08:21a 571,259 commons-collections-3.2.jar 05/22/2007 08:28a 33,976 commons-dbutils-1.1.jar 05/22/2007 08:22a 139,966 commons-digester-1.7.jar 05/22/2007 08:21a 71,442 commons-discovery-0.2.jar 05/22/2007 08:23a 279,781 commons-httpclient-3.0.1.jar 05/22/2007 08:21a 83,613 commons-io-1.3.1.jar 05/22/2007 08:22a 285,104 commons-jxpath-1.2.jar 05/22/2007 08:17a 245,274 commons-lang-2.3.jar 05/22/2007 08:27a 180,792 commons-net-1.4.1.jar 05/22/2007 08:21a 62,086 commons-pool-1.3.jar 05/22/2007 08:25a 38,830 cryptix-jce-api-20050328.jar 05/22/2007 08:25a 296,386 cryptix-jce-provider-20050328.jar 05/22/2007 08:25a 30,258 cryptix-message-api-20050405.jar 05/22/2007 08:25a 276,885 cryptix-openpgp-provider-20050405.jar 05/22/2007 08:25a 16,652 cryptix-pki-api-20050405.jar 05/22/2007 08:22a 486,522 dom4j-1.4.jar 08/08/2007 01:41p 6,205 ds.txt 05/22/2007 08:22a 19,759 geronimo-ejb_2.1_spec-1.0.1.jar 05/22/2007 08:21a 36,396 geronimo-j2ee-connector_1.5_spec-1.0.1.jar 05/22/2007 08:22a 19,259 geronimo-j2ee-management_1.0_spec-1.0.1.jar 05/22/2007 08:25a 34,263 geronimo-jaxrpc_1.1_spec-1.0.1.jar 05/22/2007 08:23a 31,397 geronimo-jms_1.1_spec-1.0.1.jar 05/22/2007 08:21a 14,637 geronimo-jta_1.0.1B_spec-1.0.1.jar 05/22/2007 08:25a 8,097 geronimo-qname_1.1_spec-1.0.1.jar 05/22/2007 08:25a 24,611 geronimo-saaj_1.1_spec-1.0.1.jar 05/22/2007 08:22a 82,923 geronimo-servlet_2.4_spec-1.0.1.jar 05/22/2007 08:25a 2,356,373 groovy-all-1.0.jar 05/22/2007 08:25a 10,832 groovy-engine-1.0-jdk14.jar 05/22/2007 08:28a 2,208,240 hibernate-3.2.2.ga.jar 05/22/2007 08:23a 386,591 hivemind-1.1.1.jar 05/22/2007 08:23a 74,662 hivemind-lib-1.1.1.jar 05/22/2007 08:23a 72,741 howl-logger-0.1.11.jar 05/22/2007 08:23a 405,545 javassist-3.0.jar 05/23/2007 08:15a 226,915 jaxen-1.1.1.jar 05/22/2007 08:28a 603,060 jbpm-3.1.4.jar 05/22/2007 08:21a 11,670 jcl104-over-slf4j-1.3.1.jar 05/22/2007 08:11a 153,253 jdom-1.0.jar 05/22/2007 08:23a 124,316 jotm-2.0.10.jar 05/22/2007 08:23a 5,798 jotm_jrmp_stubs-2.0.10.jar 05/22/2007 08:25a 11,292 jruby-engine-1.0-jdk14.jar 05/22/2007 08:25a 10,250 js-engine-1.0-jdk14.jar 05/22/2007 08:21a 31,906 jug-2.0.0-asl.jar 05/22/2007 08:20a 120,640 junit-3.8.2.jar 05/22/2007 08:25a 10,250 jython-engine-1.0-jdk14.jar 08/09/2007 08:33a 0 list.txt 05/22/2007 08:21a 367,444 log4j-1.2.14.jar 05/22/2007 08:21a 56,164 mockobjects-core-0.09.jar 05/22/2007 08:22a 148,213 mx4j-impl-2.1.1.jar 05/22/2007 08:22a 261,174 mx4j-jmx-2.1.1.jar 05/22/2007 08:22a 167,410 mx4j-remote-2.1.1.jar 05/22/2007 08:22a 485,831 mx4j-tools-2.1.1.jar 05/22/2007 08:25a 149,445 nanocontainer-1.0.jar 05/22/2007 08:24a 167,958 ognl-2.6.9.jar 05/22/2007 08:23a 682,351 org.mortbay.jetty-5.1.12.jar 05/22/2007 08:19a 65,425 oro-2.0.7.jar 05/22/2007 08:25a 112,635 picocontainer-1.2.jar 05/22/2007 08:30a 405,607 quartz-all-1.5.2.jar 05/22/2007 08:25a 251,039 retrotranslator-runtime-1.2.1.jar 05/22/2007 08:25a 14,921 script-api-1.0-jdk14.jar 05/22/2007 08:21a 12,231 slf4j-api-1.3.1.jar 05/22/2007 08:21a 6,869 slf4j-log4j12-1.3.1.jar 05/22/2007 08:30a 188,221 smack-2.2.1.jar 05/22/2007 08:23a 2,694,134 spring-2.0.5.jar 05/22/2007 08:28a 31,020 spring-modules-jbpm31-nodeps-0.8a.jar 05/22/2007 08:22a 26,514 stax-api-1.0.1.jar 05/22/2007 08:26a 113,780 stax-utils-20040917.jar 05/22/2007 08:22a 83,820 wrapper-3.2.3.jar 05/22/2007 08:26a 148,522 wsdl4j-1.6.1.jar 05/22/2007 08:22a 505,825 wstx-asl-3.2.1.jar 05/22/2007 08:28a 86,956 xapool-1.4.jar 05/22/2007 08:21a 1,212,965 xercesImpl-2.8.1.jar 05/22/2007 08:26a 131,384 xfire-aegis-1.2.6.jar 05/22/2007 08:26a 28,705 xfire-annotations-1.2.6.jar 05/22/2007 08:26a 423,888 xfire-core-1.2.6.jar 05/22/2007 08:26a 25,055 xfire-java5-1.2.6.jar 05/22/2007 08:26a 8,074 xfire-jsr181-api-1.0-M1.jar 05/22/2007 08:21a 195,119 xml-apis-1.3.03.jar 05/22/2007 08:26a 127,961 XmlSchema-1.1.jar 05/22/2007 08:21a 24,677 xpp3_min-1.1.3.4.O.jar 05/22/2007 08:22a 349,667 xstream-1.2.1.jar 94 File(s) 24,263,547 bytes
94 files make up the optional open source distribution shipped with Mule.
Writing a web-service is as simple as creating a POJO & modifying the configuration file with the right parameters.
