Dmitry Bogatov was arrested on 6 April in connection with anti-Russia protests in Moscow on 2 April.
The panel investigating the protests claims Bogatov posted several incitory messages on the sysadmin.ru forum; for example, one claim said he was asking people to bring "bottles, fabric, gasoline, turpentine, foam plastic" to Red Square, according to a post at Hacker News.
The messages were sent in the name of one Airat Bashirov and happened to be transmitted through the Tor node that Bogatov was running.
It added that messages in the name of Bashirov has continued to appear on the forum after Bogatov was arrested, with the last being on 11 April.
Bogatov, 25, is a mathematics teacher at Moscow Finance and Law University.
In a message, the Debian GNU/Linux project said it was concerned about Bogatov's arrest and hoped that he received fair treatment and due process.
"In the meantime, the Debian Project has taken measures to secure its systems by removing Dmitry's keys in the case that they are compromised," the message said.
"The Debian Project honours his good work and strong dedication to Debian and Free Software, and we hope he is back as soon as possible to his endeavours. We send our full support to him and his family."