The last official release of Melee was 3.59.4 released circa May 1999.
It was released by myself and the current "Melee Online" to do list is exactly my listing. I have not done anything with it for various reasons but I am still around. All rights were transferred by Kevin Higgins to myself in 1993, ergo, Banzai software no longer has any claim on the modern versions.
Is Melee still being developed? No. It will be resumed at some point in the future if for no other reason than "it can be".
Is it still supported? Yes. v3.59.4 Alpha is a rough port and not supported. 3.52 is available through regular BBSNET channels.
What's up with it? Well, I suppose nothing because of 10 million things. But I never gave up my rights to the software, so everything else is unofficial. Since I've yet to find a copy of 4.0 or 5.0 or "Melee Online" I cannot comment further.
For further information contact adamssw@mcmaster.ca
Thank you.
BTW the main reason it is no longer supported is due to lack of user participation. I am happy to re-open discussions and anticipate it being reborn as a McMaster University project to educate up and coming programmers. Email me with your ideas. They might happen.