Hey, Chris from Overwolf here.
Overwolf is working in cooperation with BattleEye to avoid any violation of its terms.
Please note that Overwolf doesn't have a custom crosshair app, there might be unofficial unauthorized apps, developed outside of Overwolf that we can't control (we usually block those) and I can't say that using a custom crosshair won't get you banned. However, using official Overwolf apps - will never get you banned.