Automated web GUI test tool which understands sessions

[A Seel]

I'm looking for a test tool to automate regression testing of a
BroadVision app.

The BV system puts session ids in the urls and and uses javascript to
set form actions. I'm looking for a freeware option which (ideally)
can replay user actions - without having to write scripts. The system
uses a lot of post data which would make a perl script spoofing http
gets/posts rather difficult to maintain - therefore I'd like to avoid
this option.

Commercial tools are outside of budget (for this project) although I
believe Winrunner and Loadrunner are the standard.

Freeware options I'm currently looking at are Siege and Android.

Any suggestions would be appreciated, especially from anyone who's
tried to do this with BV

Thanks

Alex