Hi. I saw in the forums that there's a way to become a VIP member without writing reviews and i'd like to know how if it's legal under the TER ToS.

Thank you

the only other way to get VIP days is to submit problem reports.  Problem reports are when you notify admin that something is wrong or missing on a provider's profile, or you find a provider with multiple profiles.  Report that and admin will combine the profiles.  You get 2 free days for each approved problem report.  Otherwise, your only option is to pay as previously mentioned.

Swim

What kind of problems do I report? I've come across some that don't have ad website links or contact infos. Would those be acceptable?

If you're trying to save the VIP monthly, you might want to think twice about hobbying. And CrazyShit don't go off on this guy, remember,  it's the newbie board!

you think is wrong with a provider's profile.  You can report duplicate profiles.  In short, anything you think is not right, report it.  It admin doesn't agree, they will not approve it.

Swim

and you do get 2 days VIP credit.  They seem to be set from European time zone...  the credits can expired before you know you have them.   Don't forget there are thousands of others doing the same thing.  I have reported some...  and not got credit because somebody else reported it before they got to my report.  
If you only want to read a PM it's fine.   If you can put the time, in you might generate a couple of leads for your bucket list.  If I'm seriously researching, I found I needed to pay.  Not necessary every month, at least not with my budget.