Hi "nrj", your partitioning scheme looks just fine to me.

> Can I use the swap for both? Does that cause any problems?
Yes & no respectively.

> Can I have two different distributions point to hda4 without any problems?
Yes

Plus you might foresee a mount point for the other distro's root FS, eg mount hda3 onto /KnopMyth when booting Knoppix, and vice versa.

Personally, I' d probably have a small hda1 for booting (plus maybe installing grub if you later want to experiment with it)- say 32Mb. All the rest can actually live within an extended partition. Also you might keep some space available and start with a smaller /home. And then 1Gb swap is a lot . You might allocate less, and if you ever temporarily need more (like when rematering), swapspace call be added in the form of regular files.

But your initial layout would work just as well ;-)