In the MCV article, Mojang's Carl Manneh is quoted saying, "The organization behind the convention support the SOPA initiative in the US. We are against it, and have no wish to support those who support SOPA, it's as simple as that. So we're not going."
SOPA never made it through Congress, and the ESA dropped support of the bill after it became hugely unpopular.
While Manneh's statement may be in line with the strict definition of the word "Boycott," it didn't quite sound like the organized effort that the word implies. Kotaku reached out to Manneh for clarification, asking him if Mojang would be boycotting or simply not attending.
"We are just not attending," Manneh replied in an email. "We didn't have any specific plans for E3 (whether or not to go), but when we found out that ESA supported SOPA we decided not to go."
It sounds like the main reasons for the indie company's non-attendance are logistical. "Since Mojang is a small company and usually brings the majority of the people when attending events, basically all development stops," Manneh said. "For that reason, we really need to prioritize what events we are attending. We think there are other events that fit our profile better. Next up, we're planning our presence at PAX Prime."
So, perhaps less a dramatic boycott and more like your or me saying, "I was going to go to the hardware store, but it's not worth the hassle and they usually don't have what I need. Plus, the owner is a jerk. I think I'll skip it."