In an update via the App Store, the notes simply state "Adobe threatened legal action unless we changed our app icon - so we did! Hope y'all like it ". The new permanent logo is yet to be revealed, but for now, the old logo has been humorously amended to avoid any potential similarities.
According to emails from developer Riley Testut sent to The Verge, Adobe's lawyers had reached out to request that a different logo be used going forward, albeit with no apparent threat issued. However, just one day later, an email from Apple suggested that the Delta app itself would be at risk of being removed, citing communication from Adobe to state that Delta was infringing on its intellectual property rights.
The developers responded to both Adobe and Apple to state that the logo was based on the stylized Greek letter 'delta', and not the letter 'A', however they pledged to change it promptly to 'avoid confusion' (and the obvious legal issues that might ensue).
So, for now, we've got a pretty wacky logo to contend with, but the Delta developers hope to have a new permanent logo ready in line with the deployment of Delta 1.6.