Hi,

is there any way to access another mods data from your own mod?

Let's I want to know if an object in near the player and that object was added via mod x.

I can only think of using SKSE with getstring from a keyword. If that object has a keyword that was added with the mod.

Another way is esmify the esp but that means my mod would have the other mod as master.

I guess other solutions don't exist?

Look at the wiki for the function GetFormFromFile. That is what you're looking for.