All these verbs relate to some sort of commercial transaction, rather than the modification per se. My read is that you could modify it freely, or even write an article documenting the save file format and how to mess with it. It's the act of commercializing the process that makes the difference between a server ban and an arrest warrant.
What is significant about this one?
Tell me you know nothing about FGO without saying you know nothing about FGO.
Microtransactions in FGO are for purchasing new characters from the gacha. "Power boosting" only comes from just playing the game like everyone else.
Source: Been playing FGO Japan since 2016, and yes I'm a whale and yes I'm happy.
I remember getting it to run on one of my devices once for a while but I was shocked at how bad the english translation was, worse than the average live action Chinese TV series.
To be fair Fate games are all about developing a strong emotional connection to the characters so I can definitely see somebody rolling a huge number of times if they want a character that they moe really hard for.