On their page it says: "## Ascensio System SIA - home of the ONLYOFFICE
ONLYOFFICE is a project developed by experienced IT experts from Ascensio System SIA, leading IT company with headquarters in Riga, Latvia. Originally ONLYOFFICE was designed for internal team collaboration.
An attempt to introduce it to a wider audience proved to be successful: ONLYOFFICE received very positive feedback from the Internet community. As a result, its functionality was considerably revised and expanded that brought about a high and stable growth of users from different countries.
Nowadays, ONLYOFFICE is an international, open source project with employees and contributors in more than 30 countries. The holding company in Singapore unites our offices around the world under the ONLYOFFICE brand. For now, we have departments in Riga, Singapore, London, Dallas, Belgrade, Yerevan and Tashkent. Would like to join our big open source family? Check how to become a contributor or discover job openings."
https://www.onlyoffice.com/about.aspx
Hmm…you seem to be at least partially right.
“In 2009, a group of software developers from Ascensio System SIA (Latvian-based) and New Communication Technologies (Russian-based) launched a project called TeamLab, a platform for internal team collaboration.[32]” https://en.m.wikipedia.org/wiki/OnlyOffice
Yeah, I was not able to convince my wife to use LibreOffice instead of Office365, but OnlyOffice was an easy sell. I really enjoy it myself as well.