I’ve only done minor testing on this but it seems to work. Give it a go and let me know.
tell application "OmniFocus"
tell content of first document window of front document
set selectedTasks to selected trees
if ((count of selectedTasks) < 1) then
display alert "You must first select tasks to search for links." message "Select a tasks from which you want to open links." as warning
return
end if
repeat with taskNum from 1 to count of selectedTasks
set curTask to value of item taskNum of selectedTasks
set paragraphCount to count of paragraphs of note of curTask
if paragraphCount > 0 then
repeat with paragraphNum from 1 to paragraphCount
set curParagraph to paragraph paragraphNum of note of curTask
if text of curParagraph is not "" then
set curLink to value of attribute named "link" of style of paragraph paragraphNum of note of curTask
if curLink begins with "App:" then
set curLink to text 6 thru -1 of curLink as string
tell application target to activate
else if curLink contains "://" then
do shell script "open " & curLink
end if
end if
end repeat
end if
end repeat
end tell
end tell