I’ve been running ClamWin AV for several years now, and Avast for 4-5 years. Only recently (after the most recent ClamWin program update) has Avast alerted on ClamWin signatures for me, and even now it’s not that often. I just did a full scan on my WinXP machine which has ClamWin AV with Avast, and Avast didn’t alert. The alerts are quite random. I haven’t yet set any exclusions in Avast for ClamWin.