The company that offers free .tk domains (DotTK ; www.dot.tk) says one accountholder can only have 3 free domains.

This means the same person can only register 3 free domains, or does it mean you can only register 3 per e-mail address ?

I have one DotTK free domain so far, could I register 2 more and that account and another one with a different e-mailadres ? (I have about 10 mailboxes)

To be frank, I don't think it's worth your time to register with different e-mail addresses. ;)

First one is only temporary until .eu is released.

Second one : I have lamatricule.com and la-matricule.com , the www.'s will be used when my site is expanded. So long I only have a MSN part at http://community.la-matricule.com

Because this is too long to be practical, I look for a redirection to use for it, until the www.'s will be launched.
So .tk looks better to me then for example come.to/lamatricule