Oh, didn't see the Java 6 requirement for Jetty 8, so Jetty 7 should be fine. I also ended up with a bunch of Jetty jars, so seems to me that the aggregate jar should be a better option.
Regarding selenium and webtests, I've been digging into it. 1 is the only thread I've regarding selenium and 2 seems to point that the Selenium server we're using supports only Firefox 1.4.1 to 2.0.0.*. Probably the same happens with IE or Safari.
So I wouldn't bet that anyone is using them, at least nowadays. As the tests can be readed/executed with latest Selenium IDE, I was thinking in going into latest Selenium Server (perhaps translating the tests into JUnit).
Also regarding the tests, they date back from a long time ago, so there's a chance that the front-end has evolved while the tests haven't, and there could be incompatibilities between them. If that's the case I would drop the tests, but not the Selenium support, we could add Selenium tests later on...