Not everyone participates in the popularity context. By some estimates about 1% of users do: There are about a quarter million popcon responses in Debian's recent popcon graphs. Absolute number of users is hard to estimate but I find one estimate of 20-50 million Debian users. So taking 1% as a lower bound, at least 18k people use StarDict in Debian. I don't know how to guess the number that use StarDict in another OS.