The easiest way to get rid of these errors, when they are not really errors, is to use a "//VALID" modifer on the tag. For example, if I have an EOEnterpriseObject named 'foo' and it will return a string from "someAttribute", then the tag below may cause a red error indicator to be displayed in eclipse, with the associated error text being: "There is no key 'someAttribute' for the keypath 'foo' in <component name>".
<wo:str value="$foo.someAttribute" />
The tag below will cause eclipse to not display this error.
<wo:str value="$foo.someAttribute//VALID" />
One may also change this behavior by chaging the values in Eclipse -> Preferences -> WOLips -> 'Binding Validation and Binding Validation Rules'. (How? TBD)