The word "Collaborationism" has negative meaning, according to Wikipedia
Collaborationism is cooperation with the enemy against one's country
in wartime.
Wikipedia also defines "collaboration" in the following manner:
Collaboration is the process of two or more people or organizations
working together to realize or achieve something successfully.
Wich doesn't sound that negative to me.
So, the question is:
Does word "collaborator" derives/associates with collaborationism or with collaboration in modern English?
I'd say in Russian it is certainly negative and is associated with "collaborationism".
Edit
Following the request in the comments I'm providing the context.
The word is used as name for subscription type on a specialized website (Trial User/Paying User/Collaborator). The website just provides economic feeds to its subscribers, so no politics here. However, the website attracts customers from all over the world.
I would replace Collaborator with Partner, just need to justify it for other members of the website administration (none of us is native English speaker).
Best Answer
Collaborator is a perfectly normal word for that purpose. If the person is actually contributing and collaborating, which they seem to do.
If you have a look at the Corpus of Contemporary English over at http://corpus.byu.edu/coca/ search for collaborator and look at the context, the overwhelming number of uses are not associated in any way with the traitorous collaborator. There are musicians, authors, chefs and people of all sorts of everyday professions that get the label collaborator.
As with every word with several meanings there is always a chance that someone misunderstands. Well, language is ambiguous. Your question is wrong in that way that there is no two words in English. There is just collaboration, the result (or action) of collaborating collaborators. All of those have both the meanings you are asking about.
Consider the amount of collaboration software and platforms out there (there are category pages on Wikipedia - which is in itself a collaboration result - about that). If your website offers any sort of collaboration possibilities in that way, I would suggest to stick to that term.
Remember, partner doesn't say anything about the type of involvement. If people work together, collaborator is the term you want. However, if they can just send in stuff individually without cooperation, maybe you can use contributor.