ALcot is a Japanese company that specializes in adult visual novels. Their first work was Clover Heart's, which was released for PC on November 28, 2003. ALcot is highly associated with the company ALcot Honeycomb, which also produces visual novels. In June 2008, there was a personal information leakage problem for their eroge Clover Hearts.
[Edited from Wikipedia]
It was founded by the Members of the Doujin circle APPLE Project.