Not only Bodu Bala Sena (BBS) but United National Party (UNP) also in Terrorism Research and Analysis Consortium (TRAC) list of terrorist groups
This is the link to the TRAC page of BBS.
TRAC has listed about 3,800 groups known to aid and abet political violence or terrorist organizations including Al-Qaeda and the LTTE, Colombo Page website mentioned .
Interestingly, the organization has named major opposition United National Party (UNP) as an inactive terrorist group that has used Assassinations as a Terrorist Tactic and Bombings. Definitely, a very accurate recognition.
No doubt, People's Liberation Front (JVP) and some other political parties like Tamil People's Liberation Tigers (TMVP) are also listed in this website due to their violent past despite they are in democratic mainstream now.