This morning I learnt that the first MySQL 5.1 development version has been released to the public.
During the last days, I successfully experimented with installing multiple MySQL servers on one machine, so this gave me the perfect preparation to download MySQL 5.1 on the db4free.net server and install it independently of the current MySQL 5.0 version that's currently in use by about 2,000 users.
It has worked fine - MySQL 5.0 continues to operate just like before and the new MySQL 5.1 version will be available via port 3307. During the weekend, I will transfer the user accounts from the 5.0 server to the 5.1 server, so - everyone who already has a MySQL 5.0 account will soon be able to access his MySQL 5.1 database as well.
You will hear about more details, soon.