Again, there's no connection between one's underlying status - whether E-2 or H-1B or L-1 - and one's green card options. Someone in E-2 status can apply for a green card. There's even an immigration form specific to those in E-2 status that must be filed with I-485 applications. The process for those who are not on a dual intent visa - that is, an H-1B or an L-1 - just needs to be thought through a bit more, that's all.