Sun ONE is the one I use and highly recommend. It is the proper
replacement for Forte I think. It's very processor and memory hungry
though, so you need a fast machine. I use an Athlon XP 1800+ with
512MB of RAM and it runs sweetly!! Its got everything Forte had with
more. Only thing is that I dont know if the free version is still
available (Sun ONE Community Edition is the free version).

Give it a try...its 120MB with jsdk1.4.1.