Little Offtopic: Database frontends

Hello,

I am sorry for this little offtopic, but recently I was looking for some
matured DB frontend. I am licensed user of Aquafold Datastudio and before
I will start to spend another money for next licenses, I would like to ask
you if there are some similar frontends out there, but with three
restrictions - Open Source, multiple DB backends, Linux port. There were
few references in history here, but most of them were comercial license
types.

The ones, I know:

ADS - non-free for commercial use.
TOra - seems to me dying GPL software. Seems to me very unstable right now
and full of hacks
SquirelSQL -missing stored procedures support, but seems interesting.

What are yours favourite?

Thank you,
Bohdan