ABC , NBC , CBS, FOX , CNN , etc all have similar rules when it comes to on air talent donating to political campaign's . You can donate but you MUST clear it with management first and this is the rule Olbermann broke . Several people at MSNBC made donations to political campaign's including Joe Scarborough but they cleared them with management first .
I believe the fact that Olbermann's ratings dropped 44 % year over year has much more to do with his demise then anything else . I understand NPR has a opening perhaps he could drag his act over there .